For a play titled Small Tragedy, playwright Craig Lucas certainly has packed in a bundle of large feelings. The current URI Theatre production (through October 19) is proving more than capable of overpowering us with them.

The challenge to engage us is immediate, since we are asked to follow the rehearsal process of actors preparing a production of Sophocles’s Oedipus Rex — with masks, no less. As backstage dramas go, this is no light-hearted 42nd Street.

But compelling interactions among the three couples, interestingly complex applications of the ancient tale to our times and temperaments, and a riveting central performance make for a production likely to leave you shaken and deeply affected.

The director of Oedipus, Nathaniel (Benjamin Gracia), couldn’t care less what we or his actors feel about the characters in the play. Fanny (Autumn Gillette) says she doesn’t un-derstand why she’s supposed to like the self-mutilating king; Jen (Jolie Lippincott) says that no, she’s supposed to pity him. The director tells them to stop thinking like that. He gets furious when he hears them discussing the characters’ motivations in contemporary terms, such as the blind soothsayer Teresias being a kind of left-wing intellectual. The play should speak for itself and the audience judge for itself, their director insists.

The concept of a tragic flaw “is crap,” he thinks, and “no more than an error in judgment,” according to his actor wife, Paola (Kira Arnold). He does convey one understanding that wouldn’t shock the Greek gods — namely that fate isn’t predestination but rather the result of succumbing to your nature, like a woman who keeps picking abusive boy-friends.

What these actors feel in the small tragedies of their offstage lives is made vitally important to them by Lucas (Reckless, Prelude To a Kiss). For example, director Nate’s pride in be-ing able to separate intellect from feelings hasn’t helped his marriage. Paola is HIV-positive, and in pre-AIDS-drugs days, she got to feel that she was taking care of him.

The play soon begins to revolve around Hajika (Benjamin Grills), and the second act lives or dies on that performance. He has recently emigrated from Yugoslavia. “Isn’t there sort of a war there?” inquires the sometimes dippy Fanny, who doesn’t even know the country is in Europe. He tells them he is a Muslim, and his eventual descriptions of the hor-rors he witnessed are hard to listen to. (“What kind of a person would tell you that?” asks Fanny, as the playwright smirks.)

Grills is terrific as Hajika, lifting this production from what should be a good one, given the material, into a marvelous one. I’ve seen him in an indifferent role in Amadeus and a challenging one in Smart Set. But here director Bryna Wortman evidently has guided him into accurately sensing when the character should be knowing but reserved and when he should break away and command the stage. If we — or the actor — don’t believe such a moment is right, to all appearances scenery is being chewed, so his self-confidence was brave.

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